RESUMO
Noncoding RNAs play regulatory roles in physiopathology, but their involvement in neurodevelopmental diseases is poorly understood. Rett syndrome is a severe, progressive neurodevelopmental disorder linked to loss-of-function mutations of the MeCP2 gene for which no cure is yet available. Analysis of the noncoding RNA profile corresponding to the brain-abundant circular RNA (circRNA) and transcribed-ultraconserved region (T-UCR) populations in a mouse model of the disease reveals widespread dysregulation and enrichment in glutamatergic excitatory signaling and microtubule cytoskeleton pathways of the corresponding host genes. Proteomic analysis of hippocampal samples from affected individuals confirms abnormal levels of several cytoskeleton-related proteins together with key alterations in neurotransmission. Importantly, the glutamate receptor GRIA3 gene displays altered biogenesis in affected individuals and in vitro human cells and is influenced by expression of two ultraconserved RNAs. We also describe post-transcriptional regulation of SIRT2 by circRNAs, which modulates acetylation and total protein levels of GluR-1. As a consequence, both regulatory mechanisms converge on the biogenesis of AMPA receptors, with an effect on neuronal differentiation. In both cases, the noncoding RNAs antagonize MeCP2-directed regulation. Our findings indicate that noncoding transcripts may contribute to key alterations in Rett syndrome and are not only useful tools for revealing dysregulated processes but also molecules of biomarker value.
RESUMO
One largely unknown question in cell biology is the discrimination between inconsequential and functional transcriptional events with relevant regulatory functions. Here, we find that the oncofetal HMGA2 gene is aberrantly reexpressed in many tumor types together with its antisense transcribed pseudogene RPSAP52. RPSAP52 is abundantly present in the cytoplasm, where it interacts with the RNA binding protein IGF2BP2/IMP2, facilitating its binding to mRNA targets, promoting their translation by mediating their recruitment on polysomes and enhancing proliferative and self-renewal pathways. Notably, downregulation of RPSAP52 impairs the balance between the oncogene LIN28B and the tumor suppressor let-7 family of miRNAs, inhibits cellular proliferation and migration in vitro and slows down tumor growth in vivo. In addition, high levels of RPSAP52 in patient samples associate with a worse prognosis in sarcomas. Overall, we reveal the roles of a transcribed pseudogene that may display properties of an oncofetal master regulator in human cancers.
Assuntos
Regulação Neoplásica da Expressão Gênica , MicroRNAs/genética , Proteínas/genética , Pseudogenes/genética , Proteínas de Ligação a RNA/genética , Transdução de Sinais/genética , Animais , Neoplasias da Mama/genética , Neoplasias da Mama/metabolismo , Neoplasias da Mama/terapia , Linhagem Celular , Linhagem Celular Tumoral , Feminino , Perfilação da Expressão Gênica/métodos , Proteína HMGA2/genética , Proteína HMGA2/metabolismo , Humanos , Estimativa de Kaplan-Meier , Células MCF-7 , Camundongos Nus , Proteínas/metabolismo , Proteínas de Ligação a RNA/metabolismo , Terapêutica com RNAi/métodos , Transcrição Gênica , Carga Tumoral/genética , Ensaios Antitumorais Modelo de Xenoenxerto/métodos , Proteínas ras/genética , Proteínas ras/metabolismoRESUMO
Current technologies have demonstrated that only a small fraction of our genes encode for protein products. The vast majority of the human transcriptome corresponds to noncoding RNA (ncRNA) of different size, localization, and expression profile. Despite the fact that a biological function remains yet to be determined for most ncRNAs, growing evidence points to their crucial regulatory roles at all stages in gene expression regulation, including transcriptional and posttranscriptional control, so that proper cell homeostasis seems to depend largely on a variety of ncRNA-mediated regulatory networks. This is particularly relevant in the human brain, which displays the richest repertoire of ncRNA species, and where several different ncRNA molecules are known to be involved in crucial steps for brain development and maturation. Rett syndrome is a neurodevelopmental disorder characterized by loss of function mutations in the X-linked gene encoding for methyl-CpG-binding protein 2 (MeCP2). MECP2 deficiency impacts globally on gene expression programs, mainly through its role as a transcriptional repressor, and growing data also points to an important dysregulation of the noncoding transcriptome in the disease. Here, we review the current knowledge on ncRNA alterations in Rett and explore links with other pathologies that might indicate the potential use of particular noncoding transcripts as therapeutical targets, tools, or disease biomarkers.
